The present disclosure relates to a method for determining a carbon dioxide content of ambient air, to a corresponding device and to a corresponding computer program.
The predominant use of CO2 sensors can be seen in ventilation and air-conditioning technology for the purpose of controlling ventilation systems depending on requirements (see, for example, the Carbocap sensors from www.vaisala.de) and in safety technology, for example for the purpose of monitoring the tightness of CO2-operated dispensing systems or fermentation cellars or cooling systems.
Typical CO2 contents are between 380 ppm to several thousand ppm in air; according to DIN EN 13779, there are four quality levels: good up to 800 ppm, average and moderate quality between 800 and 1400 ppm (0.08 to 0.14% by volume), low room air quality above 1400 ppm; the maximum immission concentration is 3000 ppm (0.3%) and the maximum workplace concentration for a daily exposure of eight hours per day is 5000 ppm=0.5%.
In recent years, virtually only NDIR measuring methods have become established for measuring CO2 in ambient air, but these measuring methods all require an adsorption section of several cm and changes in the IR source and influences of other gases must also be compensated for by means of a referencing method. There are also sensors on the market which measure the air quality by means of broadly sensitive sensors, for example from the company AppliedSensor which offers metal-oxide-based sensors for measuring CO2 equivalents (see, for example, http://www.appliedsensor.com/pdfs/APS_iAQ2000_0310.pdf). These sensors are not sensitive to CO2 at all, but rather measure the air quality and therefore indirectly also the CO2 concentration using other gases which are likewise produced when a room is used and which are also perceived as unpleasant.